Fluorescent tube lighting system



Feb. 24, 1948. NATHANSQN 2,436,399.

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 QSheets-Sheet 1 \NOUCT IVE SlDE M C NDENSAVE INDUCTI E sms: 5! 32 7 sun;

t8 e8 6 E9 3]/1: J ::3)L]1!8 19 g/ 3 sof -AR SXZZTTZANS oi?! FICLB 5,

ATTORNEY:

Feb. 24, 1948. M. NATHANSON FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 Sheets-Sheet 2 moucnve sung VOLTAGE DROP LEAD ' SCALE 3"= 10o VOLTS 3"= l AMPERE \NVENTOR MAX.NATHANSON 6T ATTIORNEYS CONDENSIVE S\DE Feb. 24, 1948. NATHANSON 2,436,399

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 Sheets-Sheet 3 E36 45 INDUCTWE (ONDENSIVE 57 44 54 53 59 SIDE Ga 48 3 J mnnnlwm'w mm WW HI um CONDENSWE SIDE \NDUCTIVE SIDE Lzl b g MAX.NATHAN5ON Feb. 24, 1948. M. TNATHANSON 2,436,399

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 SheetsSheet 4 n! 79 I conosnswz 5\DE SWE 8! CONDENSVE SDE \NDUCTVE SDE 73 7] 86 E8| 79 am y INVENTOR MAX.NATHAN$ON FIG. 6 wmwwy ATTOR NETS Feb. 24, 1948. M NATHANSON 2,436,399

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 Sheets-Sheet 5 71 CONDENSIVE S\DE 'NDUCT'VE 8| couosuswe S\DE \NDUCTlVE SIDE 5.2 Q INVEHTOR MAXJJATHANSO ATTORNEYS Feb. 24, 1948.

CONDENSIVE SIDE M. NATHANSON FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 may CONDENSIVE SIDE INDUCTIVE SlDE E169 {I l FIG. I 0

INVENTOR wazrggzwr 9 Sheets-Sheet 6 0 DE I08 1 I13 mo CTIVE 5\ m4 109 185 IE'Z 106 :05 H4 10? 0 f 98 l I 100 I I I EAO A 99 cbaaerg A TOR E Feb. 24, 1948. NATHANSON 2,436,399

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 Sheets-Sheet 7 CONDENSIVE SIDE INDUCTIVE SIDE conneuswe SIDE INDUUVE SIDE E C E146 28 6 27 E9 143 14 31 i9 ,8

' ATTORNEY Feb. 24, 1948: M, NATHANSON 2,436,399

FLUORESCENT TUBE LIGHTING SYSTEM Filed Aug. 24, 1946 9 Sheets-Sheet 8 CONDENS\VE SIDE J70 moucnve $|DE 159 e2 :79 181 79 1 115.6 1 i 155 I63 2'. I60 1 18 18g 180 I78 164 cowosnsws 510E moucnve suns I70 167 I90 INVENTOR FIG. 14 2 QZZQEZW Patented Feb. 24, 1948 UNITED STATE S PAT EN T 'OFfFJILCE 2,436,399 FLUORESCENT TUBE LIGHTING SYSTEM MaxNathanson, -Montreal, Quebec, Canada Application August 24, 1946, Serial No. 692,906

'IClaims.

.1 My invention relates .to improvements in fluorescent tube lightingsystems and is particularly useful in connection with the design and operation otdomestic and other relatively lowvoltagefluorescent tube. lighting systems in which the useot operatingyoltages substantially higher than 500-600 volts is undesirable or prohibited by..existing. regulations. In such relatively lowvoltage .systemaithe. tubes are operated in parallel with, .each...other. since the voltage required to operate two or more tubes connected in series acrossthe source .of current by a simple series connection would be prohibitively high.

.Myinvention is'based. on the theory that important economies and .other advantages can be.

achieved inlthenesign and operation of fluorescent tube lightingsystemaparticularly the relativelylowyoltagesystems previously referred to, if ltwcre possible to operate two or more of the tubes in series at a voltage substantially lower than the voltage ordinarily required for operating two or more'tubes connected in series with each other across the source 'ofcurrentby the conventional simple series connection.

In dealing with this problem of obtaining theoreticallypossible economic and other advantages by operating fluorescent tubes in series at voltages which are'substantially lower than ordinarily required and are preferably within the permissible range prescribed for operation of the previously mentioned relatively low-voltage systems, I have found a simple but far from obvious solution; More particularly I have found that this problem can be'soived in a thoroughly practical and satisfactory manner by connecting a plurality of fluorescent tubes in series with each other across a source of alternating current and providing current limiting by pass means through which current is by-passed around one of the series connected tubes to establish an ionized and conductive condition of the remaining series connected tubesand thereby enable all of said tubes to be operated in series with each other at a voltage substantially lower than would be required in the absence of said by-pass means. This is the essence of my invention and may be applied to the operation of any desired number of fluorescent tubes connected in series with each other across a source of alternating current energy having an output voltage rating substantially lower than would be adequate to operate said tubes in the absence of said current limiting by-pass means.

In .the opcration of a fluorescent tube system my invention it is important that the amount of current by-passed around one of the series connected tubes. to initla'llyestabllsh an ionized and conductivecondition oi the. remaining series connected tube '0! tubes be limited to the minimum required to establish and maintain ionization of the series connected tubes to which the bY-rPflSSBd current is supplied; In the ionized and conductive conditionoi "the :series connected tubes to whichthe 'by-passed'cun'ent is supplied, the potential acrossthe source of alternating current energy is immediate'iyfefiective to establish an ionized and conductivecom dition of the remaining tubes and to. cause surficient operating current toflow in series'throug'h all of said tubes to maintain the current density required for satisfactory operation; 'In'this 'connection it may be noted that suitable current limiting means is included in serieswlth an of said'tubes to limit the ultimate operating-current in said tubes.

Proceeding now 'to more detailed discussion of my invention reference will-be had tothe -accompanylng drawings, in which- Fig.1 is a diagrammatic elevational *v-lewoi a transformer and other componentelementsof a fluorescent lighting system embodying mydnvention.

Fig.2 is a wiring diagram of the system-shown in Fig. 1.

Fig. 2a is a vectordiagram-applicable to the system shown in Figs. 1 and 2.

Fig. 3 is a view similar to Fig. 1 but illustrating a modification of the invention.

Fig. 4 is a wiring diagram of the modified system shown in Fig. 3.

Fig. 5 is a view similar to Fig. 1-but showing a further modification.

Fig. 6 is a wiring diagram of the modified system shown in Fig. 5.

Fig. '7 is a view similar to Fig. 1 but showing a further modification.

Fig. 8 is a wiring diagram of the system shown in Fig. '7.

Fig. 9 is a view similar to Fig.1 but showing a still further modification.

Fig. 9a. is a vector diagram applicable to the system shown in Fig. 9.

Fg. i0 is a wiring diagram of the systemlshown in Fig. 9.

Fig. 11 is a view similar to Figjl but showing a still further modification.

Fig. 12 is a wiring diagram of thesystcm-shcwn in Fig. 11.

Fig. 13 is a view similar to Fig. 1 butshowing a still further modification.

Fig. 14 is a wiring diagram of the system shown in Fig. 13.

Fig. 15 is a view similar to Fig. l but showing a still further modification.

Fig, 16 is a wiring diagram of the system shown in Fig. 15.

The system shown in Figures 1 and 2 comprises three fluorescent tubes 5, 6 and I, operated by a single transformer 8, including a primary coil 9 and two secondary coils I and H.

Transformer 8 is here shown as a high leakage reactance shell-type auto-transformer having a central core leg l2 on which the three transformer coils are arranged in side by side relation with primary coil 9 lying between secondary coils l0 and I l. The central leg l2 lies between outer legs I3 and id in spaced parallel relation therewith and all of said legs are joined to end pieces l5 and I6. Primary coil 9 and secondary coil ll lie at opposite sides of high leakage reactance magnetic shunts 11.

Tubes 5 and 6 are connected in series with each other across transformer coils 9 and III while tube 1 is connected across transformer coils 9 and II. Two current-limiting condensers, l8 and I9, are suitably included in the circuit connections of lamps 5 and 6 to enable these lamps to be successfully operated in series at voltages within the permissible maximum limits prescribed for safe operation of fluorescent-tube lighting equipment.

Primary coil 9 of transformer 8 is energized by a source of alternating-current energy which maybe of any suitable voltage and frequency rate. Voltages of the order of 110 or 220 volts and frequencies of the order of 25. 50. or 60 cycles are satisfactory for practical operation.

7 In tracing the circuit connections as shown in Fig. 2 it will be noted that primary coil 9 of transformer 8 is connected across the alternatin current potential source 20 by leads 2| and 22. The left hand end of coil 9 is connected to the right hand end of coil In at junction 23. The left hand end of coil I0 is connected to the transformer side of condenser l8 b series-lead 24 and to the transformer side of condenser is by way of by-pass lead 25 which joins series lead 24 at Junction 26. The tube side of condenser I8 is connected to the right hand electrode of tube 8 by lead 21. The left hand electrode of tube 6 is connected to the left hand electrode of tube 5 by lead 28. The right hand electrode of tube 5 is connected to the right hand end of coil 9 by lead 29. The tube side of condenser I9 is connected by lead to lead 28 at junction 3 I. From this tracing of the circuit connections for tubes 5 and 6 and condensers l8 and I9, it will be apparent that condenser IS, with its connecting leads 25 and 30, provides a current-limiting bypass through which current is shunted around tube 6 and through tube 5.

In tracing the circuit connections for tube 1 it will be noted that the left hand electrode of this tube is connected to lead 29 at junction 32 and that the right hand electrode is connected to the right hand end of coil II by lead 33. The left hand end of coil H is connected, by lead 34, to the left hand end of coil 9, at junction 23.

In the operation of the system shown in Figs. 1 and 2, the input potential impressed across primary coil 9 by the source 20 of alternating current energy is increased, by transformation. to a higher output potential across coils 9 and ID. This higher output potential is maintained within the maximum limits prescribed for safe operation and. in fact, corresponds to the potential (epproximately 500 volts for a 40 watt tube) ordinarily employed for operating fluorescent tubes connected in parallel with each other.

The current-limiting condenser l9 and its connecting leads 25 and 3D afiord a high-impedance by-pass through which a limited amount of current is shunted around tube 6 to initially establish an ionized or conductive condition of tube 5.

The impedance of tube 5 is thus reduced to a value at which the voltage drop across said tube is extremely low in comparison with the voltage required to establish the ionized or conductive condition of the tube. In this connection, it will be understood that condenser 9 is designed so that its impedance is high enough to limit the flow of by-pass current in tube 5 to an amount of current which is just sufficient to establish and maintain the ionized or conductive condition of said tube. As will hereinafter be apparent this limitation of the amount of by-pass current supplied to tube 5 is necessary to keep the ultimate flow of operating current in this tube within proper limits.

In the ionized and conductive condition of tube 5, the potential across coils 9 and I0 is immediately efiective to establish an ionized and conductive condition of tube 6 and to cause suil'icient operating current to flow through the series connected condenser l8 and tubes 5 and 6 to estab lish and maintain in both of said tubes the cur rent density required for satisfactory operation. In this connection, it will be understood that condenser I8 is designed to act as an impedance, limiting current flow in tubes 5 and 5, to the current limits for which the tubes are designed. For example, in the case of a 40 watt tube, the current limit is 430 milliamperes.

For further discussion of the operating characteristics of the system shown in Figs. 1 and 2, it will be assumed that transformer 8 is designed for 110 volts, 60 cycle operation and that the wattage rating of tubes 5 and G is 40 watts. In this case. the condenser l8 should have a high enough impedance to limit current how therethrough to approximately 300 to 350 milliamperes. This amount of current will therefore flow through tube 8 in the ionized condition of the two series connected tubes but the amount of current flowing through tube 5 will be the vector sum of the current flowing through tube 6 and the amount of current flowing through the high impedance current-limiting by-pass condenser l9. For example, if the impedance of by-pass condenser I9 is high enoughio limit current flow therethrough to milliamperes, the current flow through tube 5 would be approximately 430 milliamperes which is the vector sum of the 350 milliampere flow through the main current-limiting condenser 18 and the 80 milliampere flow through the by-pass current-limiting condenser I9. Therefore, the average flow through tubes 5 and 6 will be approximately 350 ms. +430 ma.= =39!) ma.

that; in theabsence of tube and condenser i9, approximately 400 mllllamperes would be required toobtain a 40 watt'output on the 40'watt tube 6. It will therefore be apparent that operation of the tubes 5 and 6 in series has not greatly' altered the load on the transformer copper and thatnoappreciable alteration M coil ID would be required in operating two or three tubes in' series on the condensive side of the system. At this point, it may be explained that the term condensive side of the system is applied to that part of thesystem comprising tubes 5 and 6 and condensers i8 and I9 and their circuit connections as' a convenient expedient for distinguishing this part of the system from the remaining part of the system which comprises tube 1 and its-circuit connections and is hereinafter termed the inductive side of the system.

Onthe inductive side of the system the high potential impressed across tube 1 by coils 5 and I l is sufficient to efiect an ionized and conductive condition of said tube. Once current starts flowing in coil II, the high reactance of this coil and the high reluctance of the magnetic shunts i1 areeffective to limit the current flowing through tube I to the amount of current for which the tube'ls'designed.

From the foregoing description it will be seen that on one side of the system (the inductive side) there is an inductive load created by the lamp! and the high inductive reactance coil H and that on the other side of the system (the condensive side) there is a condensive load created by the tubes 5 and 5, condensers l8 and Hand coil Ill. The vectorial summation of the inductive and condensive currents which are out of phase approximately 135 is illustrated by the vector diagram appearing in Fig. 2a. This diagram, with its applied legends, is self-explanatory. and clearly shows that the sum of current flowing in the primary winding 5 is extremely high power factor with resulting reduction of copper loss and transformer heating to an appropriate minimum. In this connection it may be observed that the manner in which condensers i8 and IS are connected in circuit with tubes 5 and 6 makes it very easy to achieve a high power factor.

If the condensers l8 and i9 are combined into a single condenser unit with a tap brought out for making the common connection at junction 25, such a. unit can be made available at a cost only slightly greater than the cost of the single condenser I9.

In designing a transformer and condenser assembly for use in the system shown in Figs. 1 and 2, the only additional expense involved would be the slight extra cost for the combined condenser unit and for the slightly heavier copper required in the primary coil 9. Actual tests have demonstrated that, in a system such as shown in Figs. 1 and 2, three tubes may be operated in series with the same amount of iron required for the operation of two tubes in series. It, is therefore possible to provide a three-light instant start fixture embodying my invention at a cost approximately the same as the cost of a conventlonal three-tube hot-cathode fluorescent fixture using starters, or relays, or preheating elements in the tubes.

In connection with the foregoing discussion of Figs. 1 and 2 it will be apparent that, in the absence of the by-pass current-limiting condenser 19, approximately 1000 volts, (which is prohibited by safety regulations) would be required to oper- 6 ate the tubes 5 and 6 in series. By my method of including the condensers l8 and 19 (or other functionally equivalent current-limiting devices such as reactance or choke coils) in the circuit connections of the series connected tubes 5 and 6, it becomes possible to operate these tubes in series at a voltage of approximately 500 volts in a thoroughly practical and satisfactory manner. As previously stated, the small amount of current which condenser i9 allows to flow through lamp 5 at the available voltage of approximately'500 volts is suflicient to instantaneously establish an ionized and conductive condition of said lamp whereupon the high potential across coils 9 and ii and condenser l8 becomes immediately eifective to ionize tube 6 and to cause sufficient current to flow in series through both tubes, the impedance of condenser (8 being high enough to limit the currents in the series connected tubes to practical design limits.

The modified 4-tube system shown in Figs. 3 and 4 illustrates a feasible arrangement for operating three of the tubes in series on the conden'sive side of the system, the fourth tube being on the inductive side of the system and operated in the same manner as the previously operated tube I.

In the arrangement shown in Figs. 3 and 4 the three tubes designated 36, 31, and 38 are connected in series with each other across trans former coils 9 and Iii and the fourth tube 39 is connected across transformer coils 8 and Ii. In tracing the circuit connections shown in Fig. 4, it will be noted that a main current-limiting condenser 40, which serves the same purpose as the previously mentioned condenser I8, has its tube side connected to the right hand electrode of tube 38 by-lead 4| and its transformer side connected to the left hand end of coil ill by lead 42. The left hand electrode of tube-88 is connected to the left hand electrode of tube 31 by series-lead 43. The right hand electrode of tube 31 is connected to the right hand electrode of tube 38 by series-lead M. The left hand electrode of tube 36 is connected to the right hand end of coil 9 by series lead 45. A current-limiting bypass condenser 46, corresponding to the previously mentioned by-pass condenser i9, has its transformer side connected to the left hand end of coil Ill by lead 41 joinin lead 42 at junction 48. The tube side of condenser 45 is connected to the left hand electrode of tube 31 by lead 49 joining lead 43 at junction 50. A second current- --limiting by-pass condenser 5i similar to condenser 46 has its transformer side connected to the left hand end of coil in by lead 52 joining lead 42 at junction 48. The tube side of condenser Si is connected to the right hand electrode of tube 35 by lead 53 joining lead 44 at junction 5%.

In the system shown in Figs. 3 and 4, it is important that the transformer sides of the three condensers 40, 46 and 5! have the common point of connection represented by junction 48.

The operating characteristics of the system shown in Figs. 3 and 4 are substantially the same as described in connection with the system shown in Figs. 1 and 2. The by-pass current-limiting condensers 46 and SI allow sufiicient current to be by-passed around series-connected tube 38 to establish an ionized and conductive condition of the companion series-connected tubes 31 and 36, whereupon the voltage available across coils 9 and i0 becomes instantaneously effective to establish an ionized and conductive condition of seriesconnected tube 38 and to cause flow of sumclent current through tubes 38, 31 and 36 in series to establish and maintain satisfactory operation of said tubes, the impedance of the main currentlimiting condenser 40 being high enough to limit the operating current in the three seriesconnected tubes to practical design limits.

In tracing the circuit connections for tube 39, it will be noted that this tube is connected across the coils 9 and ll by conductors 45 and 55.

The 3-tube system shown in Figs. 5 and 6 i1- lustrates a feasible arrangement wherein inductance coils are used to operate .two of the tubes in series on the inductive side of the system.-

The transformer generally indicated at 59 in Figs. 5 and 6 is shown as a high leakage reactance shell-type transformer comprising a primary coil 60 and three secondary coils GI, 62 and 63. The four coils are arranged in side by side relation on a central core leg 64 lying between and parallel with outer legs 65 and 66, all of said legs being joined to end pieces 51 and B8. Coils 60 and BI are arranged on leg 64 at one side of high leakage reactance magnetic shunts BS. The remaining coils 62 and 63 are arranged on leg 84 at the opposite side of said shunts.

On what may be termed the condenslve side of the system shown in Figs. 5 and 6 a fluorescent tube 1| is connected across coils 6B and BI in series with a current-limiting condenser I2. In tracing the circuit connections of tube H, as 11- lustrated in Fig. 6, it will be noted that primary coil 60 is connected across an alternating current potential ource 13 by leads H and 15. The left hand end of coil 60 is connected at junction 15 to the right hand end of coil 6|. The left hand end of coil GI 15 connected to the transformer side of condenser 12 by lead 11. The tube side of condenser 12 is connected to the left hand electrode of tube 1| by lead 18. The right hand electrode of tube II is connected to the right hand end of coil 60 by lead 19. The condenser I2 is charged by the high voltage secondary coil GI and serves as a current-limiting device for the current which is supplied to tube II to establish an ionized, conductive, and luminescent condition of said tube.

On what may be termed the inductive side of the system shown in Figs. 5 and 6, a pair of fluorescent tubes BI and 82 are connected in series with each other across the coils 60 and 62 by circuit connections which may be traced as follows:

The left hand end of coil 62 is connected by lead 83 to the left hand end of coil 50 at junction 16. The right hand end of coil 62 is connected by lead 84 to the left hand electrode of tube 82. The right hand electrode of tube 82 is connected to the right hand electrode of tube 8| by lead 85. The left hand lectrode of tube 8| is connected to the right hand end of coil 59 by lead 85 joining lead 19 at junction 81.

The left hand end of coil 63 is connected to the right hand end of coil 62 at junction 88. The right hand end of coil 63 is connected to the right hand electrode of tube ill by lead 89 joining lead 85 at junction 90.

From the foregoing description of the tube connections on the inductive side of the system shown in Figs. 5 and 6, it will be apparent that tubes Bi and 82 are connected in series across the coils BI and 62 by way of series-leads B4, B5, 86 and I5. Coil 63 is a high impedance coil which, when connected as herein described. provides a high-impedance current-limiting by-pass 8v through which a limited amount of current is shunted around tube 82 to initially establish an ionized and conductive condition of tube 8 The impedance of tube 8| is thus reduced to a value atwhich the voltage drop across said tube is extremely low. in comparison with the voltage 111-1 itially required to establish an ionized and conductive condition of said tube. When an ionized and conductive condition is established in tube 8| by the small amount of ionizing current supplied to this tube by way of by-pass coil 83, the voltage available across coils BI and. 62 is immediately effective to establish an ionized and conductive condition of tube 82 and to cause sufficient current flow through the series connected tubes 82 and BI to establish and maintain in both of said tubes the current density required for satisfactory operation. In this connection it may be explained that coil 62 is a high inductance coil which serves, in conjunction with the magnetic shunts G8. to limit the operating current in the series .connected tubes 82 and BI to practical design limits. 7

The system shown in Figs. 7 and B is similar to that shown in Figures 5 and 6 with the exception of a modification of the circuit connections of the coils 62 and 63 and the series connected tubes 8| and 82.

Referring more particularly to Fig. 8, it will be noted that the left hand end of coil 62 is connected, by lead 83, tothe left hand end of coil 60 at junction 16 and that the left hand end of coil 63 is also connected to lead 83 at junction 9 l The right hand end of coil 62 is connected to the right hand electrode of tube 82 by lead 92. The left hand electrode of tube 82 is connected to the left hand electrode of tube 8| by lead 93. The right hand electrode of tube 8| is connected to the right hand and of coil 60 by lead 94 which joins lead 19 at junction 81. The right hand end of coil 63 is connected to the left hand electrode of tube 8| by lead 95 which joins lead 93 at junction 95.

In the system shown in Figs. 7 and 8, a high voltage is impressed on tube 8| through coil 53 which is wound directly on coil 62 and suflicient bleeder current flows through coil 63 to establish an ionized and conductive condition of tube 8|. When tube 8| is ignited, the reactance of coil 63 limits the current in said tube to a value just sufficient to maintain ionization and current flow. The resulting drop in the impedance of tube 8| enables the voltage generated in coil 62 to establish an ionized and conductive condition in tube 82 and to cause sufficient current flow through both of the series connected tubes 82 and 8| to establish and maintain in both of said tubes the current density required for satisfactory operation. The coils G2 and 63 shown in Figs. 7 and 8 are designed so that they are efiective, in conjunction with shunts 69, to limit the operating current in tubes 82 and BI to the proper value.

The four tube system shown in Figs. 9 and 10 illustrates an arrangement wherein a standard transformer is used in conjunction with current limiting condensers to operate two tubes connected in series with, each other on the condensive side of the system, the two remaining tubes being operated in series with each other on the inductive side of the system through the agency of suitably connected external reactancc coils.

The transformer generally indicated at 9B in Figs. 9 and 10 is shown as a standard shell-type transformer comprising a primary coil 99 and a secondary coil I00 arranged in side by side relation on a-central core leg IOI lying between and parallel with outer legs I02 and I03, all of said legs being joined to end pieces I04 and I05. As hereinafterdescribed this transformer is used in conjunction with current-limiting and I01 to operate the tubes I08 and I09 in series with each other on the condensive side of the system. Apair of reactance coils H and III are designed and connected as hereinafter described to operate the tubes [I2 and H3 in series with each other on the inductive side of the system.

The transformer unit 98 and the inductive coil unit II4 are completely separate and distinct units in the sense that they are not mechanically connected in any manner whatsoever, the inductive coil unit II4 being a complete unit with its coils H0 and III and iaminations mechanically separate from the coils and iaminations of the transformer unit.

In tracing the circuit connections of the system shown in Figs. 9 and 10 reference will be had particularly to Fig. 10 in which these connections are best shown. The primary coil 99 of transformer 98 is connected across any suitable source of alternating current energy IIIi byleads "1 and H0. The left hand end of coil 99 is connected to the right hand end of coil I00 at junction "9. The left hand end of coil I00 is connected to the transformer side of the main current-limiting condenser I06 by lead I20. The left hand end of coil I00 is also connected to the transformer side of by-pass condenser I01 by lead I2I which joins lead I20 at junction I22. The tube side of condenser I06 is connected to the right hand electrode of tube I09 by lead I23. The left hand electrode of tube I09 is connected to the left hand electrode of tube I08 by lead I24. The right hand electrode of tube I08 is connected to the right hand end of coil 99 by lead I25. The tube side of condenser I01 is connected to the left hand electrode of. tube I09 by conductor I26 which Joins conductor I24 at junction I21. This completes the tracing of the circuit connections of the two tubes connected in series with each other on the condensive side of the system and it may be noted here that the condensers I06 and I01 correspond, respectively, to the condensers I0 and I9 shown in Figs. 1 and 2 and have substantially the same functional characteristics. The by-pass condenser I01 enables a small amount oi current to be shunted around tube I09 to establish an ionized and conductive condition in tube I08 whereupon the voltage available across the coils 99 and I00 is immediately efiective to establish an ionized and conductive condition of tube I09 and to effect the required flow of operating current through the tubes I09 and I08 in series.

In tracing the circuit connections on the inductive side of the system shown in Figs. 9 and 10, it will be noted that the left hand end of inductive coil H0 is connected by lead I29 to lead I20 at Junction I22. The right hand end of coil H0 is connected by series-lead I30 to the left hand electrode of tube I I3. The right hand electrode of tube 3 is connected to the right hand electrode of tube IIZ by lead I3I. The left hand electrode of tube H2 is connected by conductor I32 to lead I25 at junction I33. The left hand end of coil III is connected. by lead I34, to lead I29 at junction I39.

It will thus be seen that the left hand end of coil III is connected by leads I34 and I29 to lead I20 at junction I22, to which the transformer sides of condensers I and I 01 are also commonly condensers I05 connected. The right hand end of coil III is connected to the right hand electrode of tube M2 by lead I40 which joins lead I3I at junction Ni.

0n the inductiveside of the system shown in Figs. 9 and 10, the inductive coil III is an extremely high reactance coil which. with its connecting leads, affords a current-limiting by-pass through which a. small amount of current is shunted around tube II3 to establish an ionized and conductive condition of tube 2. Once this condition of tube H2 is established, the voltage generated in coil H0 is effective to establish an ionized and conductive condition of tube sand to cause a limited amount of operating current, sufllcient for satisfactory operation. to flow in series through tubes H3 and H2. In this connection, it may be explained that coil IIO, when connected as herein described, functions as a limiting reactor or choke coil to maintain-the proper operating current in tubes H3 and H2 in the ionized and conductive condition of said tubes.

In the system shown in Figs. 9 and 10 the currents on the condensive and inductive sides of the system are out of phase with the voltage,

the current on the condensive side being approximately leading and the current on the-inductive side being approximately 90% lagging. The addition of these two current is diagrammatically illustrated in Fig. 9a which shows that the resultant current is lower than the currents flowing through each lamp circuit individually. The net result of this is that the current flowin in the transformer secondary coil I00 is very low as indicated on the vector diagram (Fig. 90) by point 52 and the heating of the transformer is proportionately reduced.

The 4-tube system shown in Figs. 11 and 12 illustrates an arrangement wherein two of the tubes are operated in series with each other on the condensive side of the system in the manner described in connection with Figs. 1 and 2, the two remaining tubes being operated in series with each other on the inductive side of the system through the agency of a single external inductance or choke coil.

The condensive side of the system shown in Figs. 11 and 12 is the same as the condensive side of the system shown in Figs. 1 and 2 and the component elements, including the elements of the transformer. are correspondingly numbered.

0n the inductive side of the system shown in Figs. 10 and 12, a pair of tubes I42 and I43 are operated in series with each other by means of suitable instrumentalities and circuit connections which will now be described with particular reference to Fig. 12.

The right hand end of the secondary transformer coil II is connected to the left hand electrode of tube I43 by series-lead I44. The right hand electrode of tube I43 is connected to the right hand electrode of tube I42 by serieslead I45. The left hand electrode of tube I42 is connected to the right hand end of transformer coil 9 by lead I46 which joins lead 29 at junction 32.

The left hand end of an external inductance or choke coil I41 is connected to junction 20 by lead I48. The right hand end of coil I41 is connected to the right hand electrode of tube I42 by lead I49 which joins lead I45 at junction I50.

The operation of tubes 5 and 6 in series with each other on the condensive side of the system shown in Figs. 11 and 12 is accomplished in the manner previously explained in connection with F1 the operation of thecorrespondingly numbered tubeson thecondenslve side-of the-system shown In-Fies: land 2.

On-the inductive side of'the' system sliown'in Figs:11 andlzi the-external inductance orchoke IW'and its connecting leads-provide a"currentlimiting bypass throughwhich a limited amount of current is shountedaround tube-I43 toestablish an ioni'zedand conductive condition of tube I 4-2: Atthis point it may'b'enotedthat the potentialacross points 2B-and 32 between which the tube-l42 and will l! are connected "in series witheachother-across-coils-S and I is high enough to eifectionization and current flow in tube I42, the amount 01! 'such' current flow being restricted by coil I4-I- to the minimumrequired toestab'llslr and maintain ionization of tube I42. In the'-ionized-*conditionof tube- I42, the second ary transformer coil II; acting'as-anauto-transformer-in conjunction with primary coil 9; is eiiective in conjunction with shunts I I; to-establish an ionized and conductive condition oftube I Ii -and to cause-the proper amountot operating current to'-'fl? w in both'of'tlie-serleswonnected' tubesdfl and I42;

A'ssumlflg that the =series'-connected tubes-' I42 andf are 4ll watt tub'es" and that the'coil I" and its connecting leads I '48 and II 9 are omitted; the woitager required to operate said' tubes in series woulz? be ab'out=900 volts. on the otherhand, the connectionof coil HT across polnts'ztand' 32'- in serles=wltli tube- It'l -and in parallel with tube I43 J reduces 'the' voltage required'to operate. the two tubes In series-to a.- value of-approxi matelyfiflllrolts:

The-three-tube=system shown In Figs. 13" and 14 illustrate an arrangement-whereintwo-tub'es are operated'inseries with each other on' the inductlve' side of the system in parallel with a' single' tube-connected' inserles with a currentllmitlng condenser on' the condensive' side of thesystem.

The 'transfonner generally indicated at IFS-in 1-3 and 14 isshowrr as a standard transformer 'comprlslng a-primary coil I56and'a secondary coil I51 arranged on a-central core leg I58 lying between outerlegs I59 'and- IE0, all'of said legs'beingioined to end pieces IBI and I62.- Primary. coil I56-ls connected across a source of" alternatlng 'current potential I83by leads I5! ancl'I65:

Onthecondenslve sideof the system shown In Figs; 18 and 14 a singletube IBI'ls connected acrosscoils I55'and Isl-in series with a currentlimiting condenser I68. In tracing the circuit connections ofthis tube, it will be noted that the left hand end of coil I51 is connected to'the transformer side ofcond'enser I88 by'lead' I69. The tube-side of condenser IBB'is connected to the left hand electrode of tube IB'I by lead I10. The right handeiectrode of tube IE1 is connected to the rlght'hand end of coil 158 by lead "I. The left hand'end of coil I55 is connected to the right hand endbf'coll I5Tat junction I12;

On the inductive side of the system shown in Figs. 13 and 14, two tubes IN and I are operated'inseries with each'other through the agency of'two external choke or inductance coils IIS and Ill which are mechanically separate from each othcrand from transformer I55. As here shown each ofthe coils llfi and Ill is arranged on a central'legilll lying between outer legs I15 and IE0 allof'said'legs being joined to end pieces Illl and I822 GoillTli l connected across transformer coil I58 and I51 in series with bothof the lamps IN i2 and I15." Coil I "is connected across transformer: coils I56 and" I51 in series witli-tube I" and' im para1iel=with tube I155 The circuit"connections by whichthis is"accomplishedmay-be-traced'es follows:

The right hand*endof coiFIIIHFig; 14) iscon nected, at junction-I84: to-the righ't hand c'nd of lead I85? The=lefthandend or leadllsi is-con;--

nected'to'leadIBli'atjunctiOn-MGS Th'eleft h'and a proper'value by thecurrent llmitibg efieot or condenser I885 V on the inductive side of 'the system' sliown in Figs; 13 and 14a lii'gli voltage is'impressed on' tul5e= IM 'anda small amount-ornament; Just suifici'ens to establish andmaintain unionized antf'condllmtive condition; is allowed to flow through this tube by way of the current limiting-liy-pass'afl'ordd by the-coil IIIandits oonnectingleadsr connection; it may benoted that tiiereactance'of coll I'I'IIs highenouglr-to limit the-bypass new rent in tube II I' to the minimum" requiredto maintain ionization;

O'nce current flow ls-establisliedfintube-I the voltage'across tube I15 i's'efictfie toestablish an ionized and conductive condition-oftubeIIB and to cause the properamountofoperatintcflrrent to new In both of theseseries connectd tubes-the coil IIG'being designed to actas cement-limiting" reactor which" malntaihstliecurrent' flbw in-the' series-connected tubes II I andIIWWithIn-therequired limits. Intheabsence-of! the current limiting by-passprovidedby coll ITFandJts'con' ncctions, a prohibitively hlgh-voltagewould he required to operate tubes I'Mand II5'-i.n series:

In a system such asshown in Figs; 13 and 14 a power factor closely approaching; unity canreadily be obtained'by properdesign. since the current in the transformer secondarycOiLISI' is, approximately at the lowvalue indicated by point 52 on the vector diagram shown in Fig: 9a.

The system shown In Figs. 15 and 16 Illustrates. an arrangement wherein three tubes I94, I and I96, are operated in series with each other by means of transformer I91 and three external'reactance coils I98, I99'and 200, said reactance coils. being mechanically separate from each other and. from transformer I91.

Transformer I91 15 shown as a standard shelltype transformer having a primary coilZDI and. a secondary coil 202 arranged on a central core leg 293 Lying between outer legs 204 and 205, a1l of said legs being joined to end pieces 2B6 and'ZllI'.

Each of the reactance coils I9B.. I99 and Zlill is mounted on a separate core structure including a central 13g 208 encircled by the coil and lying between outer legs 209 and 2 I0, all'of sald'legs being joined to end pieces 2 and 2I2.

In tracing the circuit connections shown in Figs. l5 and l6, it will be noted that primary coil 20I or transformer I91 is connected across a source of alternating-current energy 2 by leads 2I5 and 2I5. The left hand end of primary coil 2III is connected to the right hand electrode of tube I94 by lead 2Il. "The left hand electrode of tube IM-is connected to the left hand electrode of tube [95 by lead 2I8. The right hand electrode of tube I95 is connected to the right-hand electrode of tube I99 by lead 2I9. The left hand electrode of tube I96 is connected to the right hand end of reactance coil I98 by lead 229. The left hand end of reactance coil I98 is connected. at junction 22I. to the right hand end of the transformer secondary coil 202. The left hand end of secondary coil 292 is connected, at junction 222, to the right hand end of primary coil 2III.

The left hand ends of reactance coils I99 and 200 are connected to the right hand end of secondary coil at junction 22I by leads 222 and 224. the lead 223 joining lead 224 at junction 225. The right hand end of reactance coil I99 is connected to the right hand electrode of tube I95 by lead 226 which joins lead 2 I 9 at junction 221. The right hand end of reactance coil 209 is connected to the left hand electrode of tube I9l by lead 229 which Joins lead 2I8 at junction 229.

In the operation of the system shown in Figs. and 16, the reactance coils I99 and 209 and their connecting leads afiord current-limiting bypasses through which current is by-passed around tube I96 to effect an ionized and conductive condition of tubes I94 and I95. When this occurs the transformer volta e applied across tube I95 ls Immediately effective to establish an ionized and conductive condition of tube I96 and to cause the proper amount of operating current to flow through the three tubes in series.

The coils I99 and 209 are high reactance coils designed to limit the amount of by-pass current supplied to tubes I95 and I94 to the minimum required to establish and maintain an ionized and conductive condition of said tubes. The coil I95 is designed to act as a limiting reactor which functions, in the ionized and conductive condition of the three series connected tubes, to limit the operating current to the proper value.

In the foregoing I have described, merely by way of example. various thoroughly practical arrangements whereby the basic principles of my invention may be applied, economically, to effect instantaneous starting and operation of seriesconnected fluorescent tubes without employing operating voltages in excess of those permitted by existing safety regulations. Among other benefits flowing from the instantaneous operation of fluorescent tubes in series, in accordance with the principles of my invention, the following may be noted as being of particular importance:

(1) The cost of an instantaneous start fluorescent tube llghting fixture in which certain or all of the tubes are operated in series in accordance with my invention is substantially less than the cost of other instantaneous start fixtures having the same number of fluorescent tubes and is. in fact, the same or not substantially greater than the cost of comparable conventional slow starting fixtures which require starters. thermal devices. or relays. to operate satisfactorily and take six seconds or more to bring the tubes to a satisfactory condltion of luminescence.

(2) The Operation of fluorescent tubes in series. in accordance with my invention, lends itself to the use of any suitable source of alternating current energy including either standard or auto-transformers.

(3) In a fixture in which two or more tubes are operated by a single transformer, the operation of certain or all of the tubes in series in ac cordance with my invention makes it possible to easily achieve, by proper design. a power factor of over with resulting reduction of stroboscopic flicker and transformer heating to a minimum.

(4) Any kind or type of luminescent or gasfilled discharge tubes may be successfully and economically operated in series with each other in accordance with the teachings of my invention. However, cold cathode operation of the tubes Is recommended to reduce flicker and extinguishment of the arc in cold weather.

(5) Fluorescent tube lighting systems embodying my invention are characterized by good wave form; by the absence of flutter, light pulsations, or other detrimental or annoying effects visible to the naked eye: and by the rapidity with which the arc is re-struck and full brilliance of the tubes achieved when power is restored after being accidentally or otherwise shut oil.

(6) The operating characteristics 01' transformer-powered luminescent tube lighting systerns embodying my invention are such that the cost of providing the required type of transformer, condensers and/or current-limiting reactances is not appreciably greater than the cost of a conventional transformer. One of the factors which keeps the transformer cost relatively low is that the condensive and inductive sides of the system are each served by transformer windings in which only series current is flowing.

(7) Another advantage of the present invention is the elimination of the conventional starter with its combination of mechanical and electrical parts which, by reason of wear. sticking and chattering, are frequently the cause of fluttering, flickering and non-starting of the tubes.

Having thus described the nature and advantages of my invention and various practical applications thereof, it will be understood that various modifications are contemplated within the scope and spirit of the invention as defined by the appended claims.

Having thus described my invention, what I claim is:

1. In a fluorescent tube lighting system, a source of alternating current energy, a plurality of fluorescent tubes connected in series with each other across said source, and a high .by-pass impedance connected respectively to one terminal of said source and to a series connection between adjacent tubes, and a low impedance in series with all of said tubes and connected to the same terminal of said source as the first impedance, the impedances being in series across one of said tubes and being of such values that after the remainder of said tubes have become conductive the break-clown voltage will be applied to said one of said tubes. all of said tubes being operated in series with each other at a voltage substantially lower than the sum of the break-down voltages required for each tube.

2 In a fluorescent tube lighting system according to claim 1 wherein there are only two tubes in series.

3. In a fluorescent tube lighting system according to claim 1 wherein there are more than two tubes connected in series and wherein the said low impedance is in series with all of said tubes. and there is a separate bypass impedance connected to each series connection between adjacent tubes and the said same terminal.

amass 4:. A fluorescenttubezlighting system accordlng; t0.-claim 1. including additional tubeload, a transformer. having aprimary winding and two secondary windings in autos-transformer relalsionship, theprimary and one of said secondary windings constitutingthe source: of alternating current. energy for theseries connected tubes-and the other secondary and the primary winding constituting a source oi alternating current energy'for the said additional tube load.

5; In a fluorescent. tube lighting system according to. claim 1 wherein the impedances are condensers.

6; In a fluorescent tube lighting system according to claim, 1 wherein the impedances are reactance coils.

7-. A fluorescent tube. lighting system accordingto claim 1v including an additional tube load, a transformer having a primary winding and two secondary windings in auto-transformer rela- 20 tionship, the primary and one of said secondary windings constituting the source of alternating current energy for the. series 'connected tubes and 16: the other secondary and! the. primary winding constituting a source of. alternating: current energy for the said additional tube load said additional tube load having tubes connectedin REFERENCES CITED The following references are of record in the file of this patent:

UNITED STA'IES PATENTS Number Name Date:

2,056,661 Foulke Oct. 6,. 1936 2,370,633 Boucher Mar; 6., 1945 

